1. Technical Field of the Invention
The present invention relates to a magneto field type motor and a method of manufacturing it. The motor has an auxiliary pole made of a magnetic material that is arranged to an increasing magnetic flux side of a main magnetic pole, which is made of a permanent magnet, while the main magnetic pole and the auxiliary pole are fixed to a yoke via a magnet holding spring.
2. Description of the Related Art
Conventionally, a magneto field type motor fixed to an inner circumference of a yoke by using a permanent magnet as a main magnetic pole is known. According to this magneto field type motor, referring to Japanese Patent Application Laid-Open Publication No. 9-168245, for example, the revolving speed in a low current region can be raised without reducing the torque in a high current region by arranging an auxiliary pole that is made of a magnetic material (iron, for example) adjoining to a increasing magnetic flux side of the main magnetic pole. Consequently, the starting ability at normal temperatures can be raised.
In addition, with the above-mentioned conventional technology, a magnet holding spring having a “]”-like sectional shape (i.e. like three sides of a rectangle, or nearly U-shape in cross section) opened to the center of the yoke is used as a means for fixing the main magnetic pole and the auxiliary pole to the inner circumference of the yoke.
The method of fixing the main magnetic pole and the auxiliary pole to the inner circumference of the yoke using the magnet holding spring is explained below.
First, after fixing the magnet holding spring in the predetermined position of the circumference in the yoke, a magneto insertion space is secured with a jig among the magnet holding springs that adjoin each other around the circumference of the inner peripheral wall of the yoke.
Then, attachment of the main magnetic pole and the auxiliary pole is completed by inserting the main magnetic pole and the auxiliary pole in the magneto insertion space in an axial direction simultaneously, and pushing out the jig from the inside of the yoke synchronizing with an insertion operation of the main magnetic pole and the auxiliary pole.
By the way, since the main magnetic pole is magnetized when all the main magnetic poles and auxiliary poles are attached to the yoke, the auxiliary pole cannot be magnetically attached to the main magnetic pole when the main magnetic pole and the auxiliary pole are inserted in the magneto insertion space in the axial direction.
For this reason, a certain device is needed so that the main magnetic pole and the auxiliary pole do not come apart at the time of assembling.